linux/include/asm-generic/bitops/const_hweight.h
Paul Walmsley c32fa99f0b bitops: Fix signedness of compile-time hweight implementations
Enabling '-Wsign-compare' compiler warnings on code that includes
include/linux/bitops.h can generate the following warning:

  In file included from include/linux/kernel.h:10:0,
                    from <random filename>:48:
  include/linux/bitops.h: In function 'hweight_long':
  include/linux/bitops.h:77:26: error: signed and unsigned type in conditional expression [-Werror=sign-compare]

(converted to an error with -Werror)

This is due to the use of the logical negation operator '!' in the
__const_hweight8 macro in include/asm-generic/bitops/const_hweight.h.
The use of that operator here results in a signed value.

Fix by explicitly casting the __const_hweight8 macro expansion to
'unsigned int'.  While here, clean up several checkpatch.pl warnings.

Signed-off-by: Paul Walmsley <pwalmsley@nvidia.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1312180459580.30198@tamien
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2014-02-09 13:39:26 +01:00

44 lines
1.6 KiB
C

#ifndef _ASM_GENERIC_BITOPS_CONST_HWEIGHT_H_
#define _ASM_GENERIC_BITOPS_CONST_HWEIGHT_H_
/*
* Compile time versions of __arch_hweightN()
*/
#define __const_hweight8(w) \
((unsigned int) \
((!!((w) & (1ULL << 0))) + \
(!!((w) & (1ULL << 1))) + \
(!!((w) & (1ULL << 2))) + \
(!!((w) & (1ULL << 3))) + \
(!!((w) & (1ULL << 4))) + \
(!!((w) & (1ULL << 5))) + \
(!!((w) & (1ULL << 6))) + \
(!!((w) & (1ULL << 7)))))
#define __const_hweight16(w) (__const_hweight8(w) + __const_hweight8((w) >> 8 ))
#define __const_hweight32(w) (__const_hweight16(w) + __const_hweight16((w) >> 16))
#define __const_hweight64(w) (__const_hweight32(w) + __const_hweight32((w) >> 32))
/*
* Generic interface.
*/
#define hweight8(w) (__builtin_constant_p(w) ? __const_hweight8(w) : __arch_hweight8(w))
#define hweight16(w) (__builtin_constant_p(w) ? __const_hweight16(w) : __arch_hweight16(w))
#define hweight32(w) (__builtin_constant_p(w) ? __const_hweight32(w) : __arch_hweight32(w))
#define hweight64(w) (__builtin_constant_p(w) ? __const_hweight64(w) : __arch_hweight64(w))
/*
* Interface for known constant arguments
*/
#define HWEIGHT8(w) (BUILD_BUG_ON_ZERO(!__builtin_constant_p(w)) + __const_hweight8(w))
#define HWEIGHT16(w) (BUILD_BUG_ON_ZERO(!__builtin_constant_p(w)) + __const_hweight16(w))
#define HWEIGHT32(w) (BUILD_BUG_ON_ZERO(!__builtin_constant_p(w)) + __const_hweight32(w))
#define HWEIGHT64(w) (BUILD_BUG_ON_ZERO(!__builtin_constant_p(w)) + __const_hweight64(w))
/*
* Type invariant interface to the compile time constant hweight functions.
*/
#define HWEIGHT(w) HWEIGHT64((u64)w)
#endif /* _ASM_GENERIC_BITOPS_CONST_HWEIGHT_H_ */